1. Field of the Invention
This invention relates to a soldering pot or vessel incorporated in an automatic soldering machine for soldering printed circuit boards or the like.
2. Description of the Prior Art
A soldering pot or vessel incorporated in an automatic soldering machine includes a body, a nozzle and a pump. Melting solder supplied from the pump to the nozzle, is spouted upwardly from the nozzle toward a printed circuit board passing over the nozzle for the purpose of soldering. Specifically, the melting solder is flowed out under pressure from the nozzle in a conventional wave manner and contacted with the surface of the printed circuit board. A waste flow of melting solder, which has been spouted from the nozzle onto the printed circuit board but has not been effectively consumed during a soldering process, is recovered in the body for repetitive use. The melting solder collected in the housing has a relatively high temperature, for example, 200 degree-C. The waste flow of melting solder falls into the housing at a speed governed by a head or height difference so as to be mixed with a quantity of melting solder already contained therein. Since the melting solder is contacted with a large quantity of air, it becomes oxidized quickly so as to form oxides. It is preferable that such oxides, due to their degradation, be removed from melting solder, in advance of significant oxidation thereof. In some cases, however, such oxides may remain un-removed in view of economy. However, the oxides easily get caught around the nozzle. In particular, in a case where the nozzle comprises a primary nozzle and a secondary nozzle arranged in a direction in which printed circuit boards are transferred, the oxides are easily deposited between the nozzles. When a large quantity of oxides is deposited, such oxides tend to fall into the pot, or to get caught on a printed circuit board to be soldered so as to form non-soldered portions thereon, thus causing improper soldering.
In order to eliminate the above problems due to the oxides of melting solder, an old-fashioned countermeasure, for example, has been taken which is contradictory to a trend of labor-saving. Specifically, an operator is allocated to remove oxides in the soldering pot by means of a scooper net or spatula. In this regard, it is noted that the operator must remove oxides from the pot, while carefully paying attention to printed circuit boards continuously supplied to the automatic soldering machine. Thus, there is a risk that the operator may erroneously touch a printed circuit board and thereby damage it. There is also a risk that the operator may scald himself with a splash of melting solder.
The applicant has proposed, in Japanese Patent Application No. 03(1991)-8336, a soldering pot in which oxides accumulated around the nozzle are collected in a convenient area for removal, so that the oxides may be removed, without affecting a soldering operation. The soldering pot includes a housing the upper portion of which is separated by a partition plate to form a reservoir. A trough is provided adjacent to the wave soldering nozzle. The trough serves to receive therein a flow of waste melting solder and to direct it through a duct into the reservoir. Oxides, together with melting solder which have flowed into the reservoir will float on the surface thereof, so that they may be removed at an appropriate time.
The wave soldering pot described above is constructed to direct oxides, together with melting solder, into the reservoir through the duct connected to the trough. Thus, the oxides tend to adhere to the inner wall of the duct. The duct will be reduced in its width by the oxides deposited therein after prolonged time of use. As a consequence, the duct becomes blocked, thus making it impossible to recover or remove oxides. When the duct becomes narrowed to such an extent that it is almost blocked with oxides, the oxides, together with melting solder, will overflow from the trough, so as to adversely affect the soldering process. It is also noted that, since a volume of melting solder to be drawn into the wave pump is decreased, the height of melting solder waved from the nozzle may be significantly reduced, thus causing improper soldering.